Introduction

Verified against Minecraft 26.2

This is documentation of how Java Minecraft works — its systems, the data they own, when they run, and how they talk to each other — for the current version of the game and no other. It is the written half of a lecture series; each chapter is one lecture’s notes and follows one scenario through the codebase.

Three things to know before reading:

• Names, never code. Chapters name classes, methods and packages so that anyone with the decompiled source can find them in a minute. They do not reproduce the source. If you need the code, decompile the game.
• Mojang’s names. The identifiers here are Mojang’s official mappings, which the decompiled source uses. Fabric’s Yarn mappings differ; where a modder would not recognise a class under its official name, the Yarn name is noted once.
• Verified. Every backticked identifier in every chapter is checked against the stated version’s decompile before publishing. When a new version lands, chapters are re-verified and the header updated; there are no version-difference sections.